CN112280211A - PVC cable material with good carbon forming property and preparation method thereof - Google Patents

Abstract

The PVC cable material with good carbon forming property is characterized in that: the composition mainly comprises the following substances in parts by weight: 100 parts of polyvinyl chloride resin, 20-40 parts of plasticizer a, 10-30 parts of plasticizer b, 5-15 parts of flame retardant a, 5-15 parts of flame retardant b, 5-15 parts of carbon forming agent a, 5-15 parts of carbon forming agent b, 0.1-2 parts of antioxidant, 10-40 parts of filler a, 10-40 parts of filler b, 2-10 parts of heat stabilizer, 0.3-2 parts of lubricant and 5-10 parts of toughening agent. The flame retardant PVC material has high carbon forming property and compact and thick carbon layer, so that the flame retardant PVC material is in a way of advancing from the flame retardant material to the high-end market of the fireproof material, and the high flame retardant requirement of various products such as network lines, high-voltage power cables and the like containing a large amount of flammable substances at present can be met.

Description

PVC cable material with good carbon forming property and preparation method thereof

Technical Field

The invention belongs to the technical field of cable materials, and particularly relates to a PVC cable material with good carbon forming property and a preparation method thereof.

Background

Polyvinyl chloride (PVC) is a halogen-containing polymeric material. Pure PVC available on the market at present is a granular material, has high mechanical strength, has very good weather change resistance, water resistance and chemical resistance, and is a good electrical insulating material. Although polyvinyl chloride materials are sensitive to light and heat, their photo-thermal stability can be improved by adding a stabilizer (stabilizer). In view of molecular structure, PVC contains halogen, so it shows excellent flame retardant property, and on the other hand, PVC forms Lewis acid structure after removing hydrogen chloride or hydrogen free radical, so it has low carbon forming temperature.

The PVC cable material mainly comprises PVC resin and a plasticizer. When a PVC cable material combustion experiment is carried out, the plasticizer is directly combusted by following a gas-phase flame-retardant mechanism, and the PVC resin is firstly melted and then combusted into carbon. However, due to the dripping nature of the molten PVC resin, the burning of the plasticizer results in a significant volumetric shrinkage of the char and collapse and rupture of the carbon layer. This is one of the reasons why the carbon forming effect of soft PVC is much less than that of hard PVC.

It is well known that high polymer char plays an important role in flame retardancy. Generally, polymers having a high carbon formation rate have a high oxygen index. The formation of carbon itself plays an important role in thermal degradation. After the carbon is formed, an adhesive insulating carbon layer is formed on the surface of the high polymer, and the carbon layer can insulate the high polymer from flame. In other words, the cable material with good carbon formation can be more effectively flame-retardant.

The formation of PVC carbon is a rather complicated process, and the research on PVC carbon formation is relatively rare in China, and no theory can support it. At present, more researches at home and abroad are about the carbon forming performance of low-smoke halogen-free materials, and the polyolefin carbon forming is an immature theory, so that a plurality of phenomena can not be explained.

With the development of flame retardant technology, people change from pursuit of simple oxygen index flame retardance to pursuit of environment-simulated flame retardance, and the cable can still work normally when a fire disaster develops from simple flame retardance. The conventional PVC cable material in the market cannot meet the current high-end market demand. The implementation of standards such as V0 (fire rating), VW-1 (fire rating), CMR (fire rating), CMP (fire rating) and the like are all needed to further promote the research of PVC carbon formation.

The conventional phosphorus-nitrogen flame retardant has good carbon nucleation effect on low-smoke halogen-free materials, polycarbonate and engineering plastics. However, there are several problems with the use of conventional phosphorus nitrogen flame retardants inside PVC: 1. the phosphorus-nitrogen flame retardant retards the carbon forming rate of PVC, but increases the dripping degree of the PVC at high temperature, and the outer layer plastic is stretched and thinned by gravity due to dripping; 2. the plasticizer still follows a gas-phase flame-retardant mechanism during combustion, and the carbon layer is further thinned due to gasification combustion; 3. the nitrogen element forms micropores to expand the carbon layer, and the formed pores when the melt is thinner cause the carbon layer to crack or even completely break and fall off.

In view of the above, the present invention is a subject of how to design a PVC cable material with good carbon forming property.

Disclosure of Invention

The invention provides a PVC cable material with good carbon forming property and a preparation method thereof, and aims to solve the problem that the flame retardant property of the existing cable material cannot meet the requirement of a high-end market.

In order to achieve the purpose, the invention adopts the technical scheme that: 1. the PVC cable material with good carbon forming property is characterized in that: the composition mainly comprises the following substances in parts by weight:

the plasticizer a is one or more of trimellitate, dioctyl terephthalate, diisononyl phthalate and vegetable oil ester;

the plasticizer b is tetrabromobenzene anhydride ester and/or phosphate plasticizer;

the flame retardant a is one or more of antimony trioxide, silicate flame retardants and molybdenum trioxide; the flame retardant b is one or more of zinc borate, basic magnesium carbonate, silicon stannate, magnesium stannate and montmorillonite;

the carbon forming agent a is phenoxy polyphosphazene and/or hexaphenoxy cyclotriphosphazene; the carbon forming agent b is polyphenyl ether.

The following is an explanation of the present technical solution:

1. in the above embodiment, the polyvinyl chloride resin includes a polyvinyl chloride homopolymer and/or a polyvinyl chloride copolymer; the polyvinyl chloride homopolymer is suspension polymerization polyvinyl chloride, emulsion polymerization polyvinyl chloride and chlorinated polyvinyl chloride; the polyvinyl chloride copolymer comprises vinyl chloride-vinyl acetate copolymer and chlorinated polyethylene.

2. In the scheme, the phosphate plasticizer is triphenyl phosphate, tricresyl phosphate or tris (2, 3-dibromopropyl) phosphate.

3. In the scheme, the heat stabilizer also comprises 2-10 parts of a heat stabilizer, wherein the heat stabilizer is a phosphite stabilizer and/or a calcium zinc stabilizer.

4. In the scheme, 0.1-2 parts of antioxidant is also included, and the antioxidant is one or more of antioxidant 1010, antioxidant 1076, antioxidant 1024 and antioxidant 1098.

5. In the scheme, the composite material further comprises 5-10 parts of a toughening agent, wherein the toughening agent is one or more of an Elvaloy HP441 toughening agent, an alpha-methylstyrene-acrylonitrile copolymer and chlorinated polyethylene under the American DuPont brand. .

6. In the scheme, the lubricating agent also comprises 0.3-2 parts of lubricating agent, wherein the lubricating agent is one or more of stearic acid, pentaerythritol stearate, polyethylene wax, calcium stearate and oxidized polyethylene.

7. In the scheme, the vegetable oil is citric acid triester and epoxy fatty acid methyl ester.

8. In the scheme, 1-5 parts of processing modifier can be added, and the processing modifier is ACR401 and/or ATL-95.

9. In the scheme, the carbon forming agent b is polyphenyl ether with 30-40% of phosphorus and nitrogen.

10. In the scheme, the silicate flame retardant is tin silicate and magnesium silicate.

11. In the scheme, the composite material also comprises 10-40 parts of a filler a, wherein the filler a is calcium carbonate; 10-40 parts of a filler b, wherein the filler b is one or more of aluminum hydroxide, magnesium hydroxide and talcum powder.

12. In the scheme, the phosphite stabilizer and the calcium zinc stabilizer refer to environment-friendly stabilizers without lead and other heavy metal elements.

13. The preparation method of the PVC cable material with good carbon forming property is characterized by comprising the following steps:

weighing according to the proportion of the formula to obtain the raw and auxiliary materials; putting the weighed raw and auxiliary materials into a high-speed kneader, heating to 130-140 ℃ under high-speed friction, kneading at high speed, and fully mixing uniformly and preplasticizing; putting the mixture into a double-screw extruder set to perform extrusion, mixing and plasticizing at the temperature of between 130 and 160 ℃; single screw granulation at 100-130 ℃.

The design principle and the effect of the invention are as follows:

1. the polyvinyl chloride resin in the technical scheme of the invention comprises polyvinyl chloride homopolymer and/or polyvinyl chloride copolymer; the polyvinyl chloride copolymer containing the polyvinyl chloride monomer is theoretically suitable for the technical scheme of the invention, wherein the higher the chlorine content is, the more excellent the flame retardant carbon forming property is, the higher the mechanical property is, and the better the wear resistance and scratch resistance are.

2. The technical scheme of the invention uses two types of plasticizers, wherein the plasticizer a (trimellitate, dioctyl terephthalate, diisononyl phthalate and vegetable oil ester) is a conventional plasticizer and is used for reducing the conversion point of PVC glass, so that the PVC is more flexible and has more excellent processability; the plasticizer b (tetrabromobenzene anhydride ester and/or phosphate plasticizer) is a flame retardant plasticizer, belongs to a brominated flame retardant/phosphoric acid series flame retardant, can endow flame retardance while endowing PVC flexibility, pyrophosphate which can be formed in a combustion process by a phosphorus flame retardant is beneficial to forming a carbon layer, and the brominated flame retardant is characterized in that the gas-phase flame retardant effect of bromine is greater than that of chlorine, so that the gas-phase flame retardant efficiency of a product can be greatly improved.

3. The technical scheme of the invention uses two types of flame retardants, namely a flame retardant a (antimony trioxide, silicates and molybdenum trioxide) and a flame retardant b (zinc borate, basic magnesium carbonate, silicon stannate, magnesium stannate and montmorillonite), wherein the flame retardant a is a conventional flame retardant, and the flame retardant b is a filling type flame retardant, so that the material can be endowed with dimensional stability and carbon layer stability, the content of inorganic solid-phase organic matters is improved, and the carbon residue rate is improved; the two flame retardants are used together to generate a synergistic effect, so that the flame retardant efficiency is further improved, and the mechanical property of the polymer is maintained.

4. The technical scheme of the invention uses two types of carbon forming agents, wherein the carbon forming agent a (phenoxy polyphosphazene and hexaphenoxy cyclotriphosphazene) is a phosphorus-nitrogen flame retardant (phosphazene flame retardant), and the phosphorus-nitrogen heterocyclic structure and the benzene ring structure of the phosphorus-nitrogen flame retardant have higher phosphorus, nitrogen and carbon contents. The nitrogen element can be used as an air source in the combustion process, so that the carbon layer is fluffy and expanded; on the other hand, phosphorus can generate pyrophosphate or serve as an acid source to accelerate the carbon forming rate, and carbon can increase the carbon content of the system, improve the thickness of the carbon layer and reduce cracks of the carbon layer; and such organic flame retardants have better compatibility than inorganic flame retardants; on the other hand, the phosphazene flame retardant and the polyphenylene oxide (the carbonizing agent b) can form a thicker, compact and stable carbon layer together, and can effectively promote the amount of carbon formation

5. The plasticizer is the root cause of PVC's flammability and poor char formation due to its gas phase free radicals, which volatilize causing the volume-shrinking carbon layer to crack. The improvement of the oxygen index of the aluminum hydroxide is obvious, and the aluminum hydroxide is likely to be water vapor released by the decomposition of the aluminum hydroxide, expand, and simultaneously residual aluminum oxide is easy to be pulverized after being burnt and cannot effectively adhere to a carbon layer, so that the carbon layer is cracked. The carbon forming effect of magnesium hydroxide is better than that of aluminum hydroxide. The phosphazene flame retardant and the polyphenyl ether can form a thicker, compact and stable carbon layer together, and the carbon forming quality can be effectively promoted.

6. The phenoxy polyphosphazene and the hexaphenoxy cyclotriphosphazene belong to the non-volatile phosphorus-nitrogen flame retardants and follow condensed phase flame retardants. The heat absorption of phosphazene upon thermal decomposition is a cooling mechanism; phosphoric acid, metaphosphoric acid and polyphosphoric acid generated by thermal decomposition of the composite material can form a layer of non-volatile protective film on the surface of the polymer material to isolate air, which is an isolating film mechanism; simultaneously, gases such as carbon dioxide, ammonia gas, nitrogen gas, water vapor and the like are released after heating, which is a dilution mechanism; these nonflammable gases block the supply of oxygen and achieve the purpose of flame retardancy synergy and synergy, and the polymer, upon combustion, has the formation of PO-groups which can combine with H-, HO-, C-reactive groups in the flame zone to act as flame-inhibiting, which is a chain-terminating reaction mechanism. For char formation, where the phosphorus element inhibits smoldering, i.e.: smoldering of carbon, the mechanism of action is the passivation of the surface of the carbon layer covered with polyphosphoric acid, pyrophosphoric acid species and oxidizable active sites on the carbon. The nitrogen, ammonia and the like released after the nitrogen element burns can enable the carbon layer to form a porous structure, the thickness of the carbon layer is increased, and the increased thickness of the carbon layer has the advantages of increasing the distance between flame and a burning object and increasing the distance of the plasticizer from the inside to the outside. The high-carbon-content structure of the polyphenyl ether can increase a carbon source in the material, increase the thickness and the compactness of a carbon layer, reduce the permeability of the carbon layer, reduce the gasification of a plasticizer, the diffusion of combustible substances such as free hydrogen radicals and the like to the surface, and reduce the concentration of combustible substances on the surface layer. Phosphorus element can inhibit the flame retardant effect of antimony trioxide for the change of oxygen index, and the high carbon formation can also inhibit the flame retardant effect of antimony trioxide. This is likely to be the case when carbon formation forms a firm and dense carbon layer, which inhibits the formation of gaseous antimony trichloride and reduces the gaseous flame retardant efficiency. However, the oxygen index of 30 for PVC, the flame retardance reaches the flame retardance level, and meanwhile, the oxygen index has limitation on the judgment of the flame retardance of the material.

7. The phosphate ester and the tetrabromobenzene anhydride ester are obviously improved in oxygen index, have great influence on low temperature and slightly improve the carbon residue rate. The flame retardant mechanism of the tetrabromobenzene anhydride ester is a gas phase flame retardant mechanism, and mainly realizes flame retardance by capturing free radicals in air. However, bromine-carbon bond energy is lower than chlorine-carbon bond energy, and bromine radicals and hydrogen bromide are more easily generated, while hydrogen chloride, although also generated in large quantities, has a lower concentration at the flame front. Bromine is more flame retardant efficient than chlorine. And tetrabromobenzene anhydride ester contains a benzene ring structure, and the decomposed benzene ring structure can be remained in the carbon layer to form coke which is used as a fire-proof barrier. Phosphate ester plasticizers are effective flame suppressants as volatile plasticizers. The phosphate ester can be cracked into small molecules or free radicals, and the small molecules or free radicals can absorb hydrogen free radicals in a flame area and reduce the concentration of the free radicals to extinguish the flame. There is a slight effect on the carbon residue, which may be benzene rings remaining in the carbon layer, increasing the quality of the carbon layer. The oxygen index is reduced due to the antagonism of antimony trioxide and phosphorus, but the phosphorus flame retardant has high content of residual carbon, can improve the structure of a carbon layer and reduce the phenomenon of cracking of the carbon layer.

8. Polyphenylene ethers are described herein as having poor compatibility with PVC, and thus polyphenylene ethers are ground to a powder of 5-10um by low temperature crushing. Which are distributed in the matrix in a filling form and in an island-in-sea structure. Although the strength elongation is reduced, the use requirements of PVC such as: GB/T8815 UL1581 and the like.

The invention has the advantages that:

the cable material in the technical scheme of the invention has high carbon forming property, and the carbon layer is compact and thick, so that the flame retardance of PVC is advanced from the flame retardant material to the high-end market of the fireproof material. The product can meet the high flame-retardant requirement of various products such as network cables, high-voltage power cables and the like containing a large amount of inflammable substances at present, and no adversaries are found at present in China.

According to the technical scheme, the bromine and phosphorus flame-retardant plasticizers are used for replacing conventional plasticizers, the bromine improves the efficiency of a gas-phase flame-retardant mechanism, the phosphorus serves as an acid source to further promote the carbon forming speed, and the conditions of reduction, collapse and dripping of a carbon layer of the PVC material caused by the combustion of the plasticizers are reduced. And a series of carbon forming agents with high carbon and low hydrogen content are added, so that the thickness of the carbon layer is increased, the surface cracks are reduced, and the carbon forming quantity is improved. Thus enabling very flexible PVC materials to pass various types of flame resistance tests, such as: the flame retardant test such as V0, VW-1, FT-1, needle flame test and the like, and meanwhile, the conventional flame retardant property of the PVC cable is ensured to be in the way of advancing to the fireproof material, so that the cable can normally work in fire.

The technical scheme of the invention also solves the problems of poor carbon content, more cracks, incompact carbon layer and easy cracking of the conventional phosphorus-nitrogen flame retardant in PVC.

In conclusion, the PVC cable material with good carbon forming property is provided by selecting two specific types of plasticizers, two types of flame retardants and two types of carbon forming agents and through the combined action effect of the composition.

Drawings

FIG. 1 is a chart of charring by combustion and a chart of surface cracking in example 1

FIG. 2 is a chart of charring and surface cracking in example 2

FIG. 3 is a graph showing a burned carbon pattern and a surface crack pattern in example 3

FIG. 4 is a chart of char formation by combustion of comparative example 1

FIG. 5 is a combustion comparison chart of example 1 and comparative example 1

Detailed Description

The invention is further described below with reference to the following examples:

in order to more clearly and concisely describe the following embodiments, some of the materials referred to in the embodiments have been given their english reference numerals.

The related English code has the Chinese meanings as follows:

PVC is polyvinyl chloride, TOTM is trioctyl trimellitate, DOTP is dioctyl terephthalate, DINP is diisononyl phthalate, SPVC is suspension polymerization polyvinyl chloride, EPVC is emulsion polymerization polyvinyl chloride, CPVC is chlorinated polyvinyl chloride, and DPOP is diisooctyl diphenyl phosphate.

The carbon residue rate test method comprises the following steps: pressing the product into 0.5-0.6mm slices, taking a square with the size of 1.5 x 1.5cm, placing the slices on a metal plate, igniting the front surface of the metal plate by using methane gas, covering the whole slices with flame, burning for 3min at least until the surface is completely carbonized, drawing a 1.5 x 1.5 white paper frame after the carbon layer is cooled, photographing the top of the white paper frame, and recording the surface state of the carbon layer and the mass retention rate of the carbon layer.

Examples 1 to 10: a PVC cable material with good carbon forming property and a preparation method thereof are disclosed, wherein the formula of the raw materials (unit: parts by weight) is as shown in Table 1:

TABLE 1 PVC Cable Material with good char formation examples 1-5 component tables

Table 2 raw material names of the respective components used in the examples:

in the above examples, the trimellitate was Poline TM8-10, the phosphite stabilizer was diphenyl isooctyl phosphate (DPOP) and dilauryl thiodipropionate (DLTP), the calcium zinc stabilizer was bear brand 8656/9700, and the polyphenylene ether was SA9000 from Sauter base industries, Inc.

The production process is carried out once according to the following steps: preparing raw and auxiliary materials, weighing according to the formula proportion, high-speed kneading, extruding, mixing and plasticizing by a double-screw extruder unit, granulating by a single screw, cooling and sieving, and ensuring. In the kneading process, a high-speed kneader is used to heat the raw and auxiliary materials to 130-140 ℃ under high-speed friction, and the raw and auxiliary materials are fully and uniformly mixed and preplasticized; the double screw temperature is set to 130-160 deg.c and the single screw temperature is set to 100-130 deg.c, and the product is produced through double screw plasticizing, single screw pelletizing, cooling, metering and packing. The material is placed on an extruder production line with a screw diameter of 50mm, the temperature is set to be 140-175 ℃, the high-carbon-formation PVC sheath material can be obtained, and compared with common PVC, the material not only has good flexibility, but also has good flame retardance and carbon formation.

The formula and experimental result data of the common PVC flame-retardant sheath material are as follows:

formula and result for burning common PVC flame-retardant sheath material

The above embodiments are merely illustrative of the present invention and do not limit the scope of the claims, and other alternatives that may occur to those skilled in the art are also within the scope of the claims.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (8)

1. The PVC cable material with good carbon forming property is characterized in that: the composition mainly comprises the following substances in parts by weight:

100 parts of polyvinyl chloride resin;

20-40 parts of a plasticizer a;

10-30 parts of a plasticizer b;

5-15 parts of a flame retardant a;

5-15 parts of a flame retardant b;

5-15 parts of a carbon forming agent a;

5-15 parts of a carbon forming agent b;

the plasticizer a is one or more of trimellitate, dioctyl terephthalate, diisononyl phthalate and vegetable oil ester;

the plasticizer b is tetrabromobenzene anhydride ester and/or phosphate plasticizer;

the flame retardant a is one or more of antimony trioxide, silicate flame retardants and molybdenum trioxide; the flame retardant b is one or more of zinc borate, basic magnesium carbonate, silicon stannate, magnesium stannate and montmorillonite;

the carbon forming agent a is phenoxy polyphosphazene and/or hexaphenoxy cyclotriphosphazene; the carbon forming agent b is polyphenyl ether.

2. The cable material according to claim 1, wherein: the polyvinyl chloride resin comprises polyvinyl chloride homopolymer and/or polyvinyl chloride copolymer; the polyvinyl chloride homopolymer is suspension polymerization polyvinyl chloride, emulsion polymerization polyvinyl chloride and chlorinated polyvinyl chloride; the polyvinyl chloride copolymer comprises vinyl chloride-vinyl acetate copolymer and chlorinated polyethylene.

3. The cable material according to claim 1, wherein: the composite material also comprises 10-40 parts of a filler a, wherein the filler a is calcium carbonate; 10-40 parts of a filler b, wherein the filler b is one or more of aluminum hydroxide, magnesium hydroxide and talcum powder.

4. The cable material according to claim 1, wherein: the heat stabilizer is phosphite ester stabilizer and/or calcium zinc stabilizer.

5. The cable material according to claim 1, wherein: and 0.1-2 parts of antioxidant, wherein the antioxidant is one or more of antioxidant 1010, antioxidant 1076, antioxidant 1024 and antioxidant 1098.

6. The cable material according to claim 1, wherein: the toughening agent is one or more of an Elvaloy HP441 toughening agent, an alpha-methylstyrene-acrylonitrile copolymer and chlorinated polyethylene under the U.S. DuPont trademark.

7. The cable material according to claim 1, wherein: and the lubricant also comprises 0.3-2 parts of lubricant, wherein the lubricant is one or more of stearic acid, pentaerythritol stearate, polyethylene wax, calcium stearate and oxidized polyethylene.

8. A preparation method of the PVC cable material with good carbon formation property according to any one of claims 1 to 7 is characterized by comprising the following steps:

weighing according to the proportion of the formula to obtain the raw and auxiliary materials; putting the weighed raw and auxiliary materials into a high-speed kneader, heating to 130-140 ℃ under high-speed friction, kneading at high speed, and fully mixing uniformly and preplasticizing; putting the mixture into a double-screw extruder set to perform extrusion, mixing and plasticizing at the temperature of between 130 and 160 ℃; single screw granulation at 100-130 ℃.

Images